Liquid-level indicator



Nov. 20, 1928.

H. FARMAN LIQUID LEVEL INDICATOR Flled Dec 15 1924 7 mine?! jnvarr. far

Pmm Maw Patented vN03,. 20,1928.

UNITED STATES PATENT OFFICE.

HENRI 'IARMAlfI, on BILLaNcoUM, FRANCE.

LIQUID-LEVEL INDICATOR.

Application filed December s, 1924, Serial No. 756,060, and in France December 29, ices.

A commonly used device for indicating the, level of a liquid at a distance comprises a pressure responsive gage and an air pump arranged the one near the other w1th1n the a reach of the hand under observation of the f driver and connected to the reservoir containing the liquid the level of which has to be indicated.

In apparatus of known construction an in- 10 dication is obtained by pumping air into the column from 0 to 100"cm. it must be very sensitive so that by sud en variations. in pressure to which it is submitted it mlght be easily rendered inoperative. A further inconvenience of apparatus of known construction isthat, owin 7 to the difierent leakages of the conduit an of the pump, the hand of the pressure responsive gage will slowly move back to zero as soon as the-stroke of the ump has taken place and the indication so has een given.

This invention has for its object to obviate these inconveniences. With this object in view the pump and the pressure responsive gage are mounted, according to the invention, onthe end of two tubes having each a capillary bore, which are connected with one another by means of a closed tube arranged in the reservoir to be gauged, this closed tube:

forming anair dash. ot as it contains always after the stroke of t e pump, a quantity 0 air which holds the level of the liquid in this closed tube at the lower end of the capillary bore coming from the pump, the contact pressure of this air-corresponding to the hei ht of liquid in the reservoir-acting upon he pressure responsive gage which gives thus accurate and stable indications relating to the height of this level in the reservoir.

An embodiment of the invention is dia-- grammatically illustrated, by wayof example, in the only figure of the accompanying drawing. 3

Referring to the diagram-a is a reser ioir containing the liquid to be gauged. In this reservoir a closed tube 6 is arranged which has in its lower end narrow openings 0 and e an air this con the liquid will rise in the con the upper part of which communicates by a conduit (1 having a capillary bore with a pressure responsive gage. In this conduitd an air reservoir is, inserted between the ends 2 and of thecapillary bore in conduit (1. A conduit 9 having a capillary bore connects pump h with the closed tube 6 and uit g terminates close to the openings 0 in the closed tube The iston i of the-air pump is controlled bya sprlng j. The mouth k of the capillarybore of conduit g is located in the bottom plate of the air pump. The operation is as follows:

Suppose the level of the liquid to be gauged;

is at the same hei ht in the reservoir 41 and-- in the closed tube the spring will be com pressed when the piston z is bem lifted andthe body of the pump it fills wit air which flows in, not through the mouth of the capil lary bore k, which ofiers too much resistance,

but at the sides of the pistonri which are made of pressed leather. The said piston i, whenreleased, descends under the action of the spring 7' and. sends an air charge,- through the conduit g, into the lower part of the closed tube 6. This air rises in .said

clpsed tube and forces the liquid into the res-. ervoir through the openin s c, producing inthe upper hermetically c osed part of the closed tube b a pressure which is always equal to the difference of the liquidleVeI in the reservoir and in the closed tube. I

This pressure, which reaches the maximum when the air forced in by pump h begins to flow out of the closed tube 6 t rough the openings 0, is trans itted to the pressure responsive gage e w ch indicates the height of the corresponding liquid level.

The small air reservoir 7' of any known type, in the capillary bore "of the conduit d serves to regulate the execessive pressures rethe reservoir.

In a device of this ty e, the pressure re- :pon'sive gage e is there ore separated from e pump it bythelong conduits d and e.

sulting fromthe oscillations of the liquid .in

I Further the pressures, before arrivinglin the pressureiresponsive gage 6, must pass t rough several capillary conduits and through a closed tube in which the air volume varies not.

It will therefore be protected against the sudden shocks originating from the pump.

On the other hand, the stabilization of the pressure responsive gage is obtained by the fact that, if there is any leakage in the pump, uit 9 until the equilibrium of the levels is established, but it could never rise in the annular space of the closed tube 1) higher than the lower orifice of the conduit g. This annular space of the closed tube will therefore remain filled with air at the pressure produced by the height of the liquid column. Even if one supposes that the pump be suppressed and the conduit 9 open to the atmosphere, the pressure responsive gage will always indicate the same level and will thus be stabilized.

I claim:

An apparatus designed to indicate at a distance the position of the level of a liquid 3 comprising in combination with a reservoir containing the liquid, an air pump, a pressure responsive gage, a tube, closed at each end, extending downwardly in said reservoir to adjacent the bottom thereof and provided with openings in its side walls near the lower end thereof for communication with the liquid in said reservoir at the minimum level to be gaged, a tubular conduit of capillary bore, connected at one end to said pump and extending downwardly in said tube and terminating a short distance above the bottom thereof and a second conduit having a capillary bore and connecting the top end of said closed tube with said pressure responsive gage.

In testimony whereof I afiix my signature.

HENRI FARMAN. 

